Three extensive mountain systems, running north and south, give rise to at least eight topographic subdivisions of the country, going from east to west. 1. The narrow belt of level coast and hill country along the Atlantic shore, from 100 to 200 miles in width with elevations up to 1,000 feet, but especially low along the seacoast from Virginia south; drained by short rivers navigable only for short distances from the mouth; a farming country, with the soils varying from the richest to the poorest; some 300,000 square miles. 2. The Appalachian mountain country, nearly of the same width as the first section, with elevations up to 5,000 feet; the watershed of all the rivers to the Atlantic, of several rivers to the Gulf, and of the eastern affluents of the Mississippi; a mountain country, of about 360,000 square miles extent, rich in coal, iron and other minerals, except in its northern extension formed of archean rock. 3. The great river basin of the Mississippi, a Central plain of glacial and river deposit, rising gradually from the Gulf to the headwaters for more than 1200 miles, and nowhere over 1,000 feet above sea level; the richest agricultural section, 700,000 square miles, more or less, in extent. 4. The plateau, rising towards the Rocky Mountains from 1,000 to 5,000 feet above sea level, some 870,000 square miles in extent, a region of scanty rainfall, hence of prairie and plain, but mostly rich soil of undetermined depth, capable of prolific production where sufficient water supply is available. 5. The Rocky Mountain region, rising from 5,000 to near 10,000 feet (except some higher peaks), an arid to semi-arid district of rugged ranges, covered mostly with forest growth, often open and of inferior kind, with tillable soils in the narrow valleys, requiring irrigation for farm use; a mining country, rich in gold and silver, extending over 150,000 square miles. 6. The Sierra Nevada Mountain Range, including the Coast Range, rarely over 7,000 feet elevation, arid to semi-arid on the Eastern slopes; humid, and supporting magnificent forest growth on the Western slopes; some 190,000 square miles. 7. The Interior Basin, lying between the two preceding mountain ranges, some 400,000 square miles; for the most part a desert, although in parts supporting a stunted growth of pinon and juniper, and, where irrigation is possible, productive. 8. The interior valleys of the Sierra, comprising about 30,000 square miles, which, under irrigation, have become the garden spots of the Pacific. To these topographic subdivisions correspond in part the climatic and the forest conditions, although variation of soil, and of northern and southern climate produce further differentiation in types, and in distribution of field and forest.